The present invention relates to a track compensation apparatus in a magnetooptical disk apparatus, and more particularly, to an apparatus for compensating a track when a track crossing signal is not generated due to an offset detection flag region or a defect of the disk.
Generally, the magnetooptical disk apparatus utilizes a track crossing signal which is generated when an optical beam passes over the surface of a disk to count the number of tracks. Also, unless the number of tracks is accurately counted, the location of the optical beam cannot be identified, nor can the target track be swiftly accessed.
The conventional magnetooptical disk apparatus detects a movement distance of a photo beam by possessing a linear scaler in order to move the optical beam to a target track. However, since the track width of the conventional disk is 1.6 .mu.m and the width of the linear scaler is quite large relatively, that is, 80 .mu.m, it is difficult to move the optical beam to a target track accurately.
Another conventional magnetooptical disk apparatus does not use the linear scaler, and utilizes a direct seek method for directly counting tracks using a track crossing signal.
FIGS. 1A through 1C are waveform diagrams in connection with a track crossing signal in a magnetooptical disk apparatus using the conventional direct seek method. FIG. 1A shows a trace of a photo beam which passes over the surface of a disk. FIG. 1B is a track crossing signal. FIG. 1C is a signal obtained by performing the binarization of tile track crossing signal of FIG. 1B.
In FIG. 1A, an offset detection flag (ODF) region represents the location of a mirror for correcting tile tracking error offset, as a one-byte area of one sector on the disk. If the photo beam passes through the ODF region, a distorted signal having a non-sinusoidal waveform is generated as the track crossing signal as shown in a portion "d" of FIG. 1B. Finally, as shown in FIG. 1C, since a track crossing binarization signal is not produced, the number of the tracks cannot be accurately counted.